In both humans and rats dopaminergic drugs can facilitate male sexual behavior; however, systemically administered drugs affect many systems simultaneously. The proposed experiments will first determine the sites and pharmacological specificity of dopaminergic influences in intact animals. They will then test the effectiveness of facilitative treatments in restoring copulation in animals deprived of their olfactory sense or gonadal hormones. Finally, the relationship of endogenous dopamine activity to copulatory ability of castrates will be determined. The specific aims of this project are to: (1) Determine the types and interactions of dopamne receptors in the medial preoptic area that influence copulation of male rats. Drugs specific to the D1 and D2 receptor subtypes will be microinjected into this area immediately before sexual behavior tests. (2) Determine whether dopaminergic synapses in four other areas (nucleus accumbens, ventral tegmental area, bed nucleus of stria terminalis, lumbar spinal cord) affect copulation. A dopamine agonist and/or antagonist will be microinjected into these sites before sexual behavior tests. In addition, specificity to sexual motivation, rather than motor activation, will be tested using a conditioned place preference test. (3) Compare dopaminergic influences on copulation with those on reflexive penile responses. Similarity of effects will suggest that the effects of dopaminergic drugs on copulation may result in part from increases or decreases in reflexive mechanisms. (4) Test the effectiveness of the dopamine agonist apomorphine injected into the five sites noted above in restoring copulation in anosmic male rats. (5) Test the effectiveness of apomorphine injected into those sites in restoring copulation in castrated rats. (6) Determine whether endogenous dopamine activity in those sites is related to the ability of castrates to copulate. Dopamine activity in several brain areas will be assayed and compared with copulatory ability in castarated male rats. Since many of the mechanisms subserving masculine function are shared by numerous mammalian species, and since dopaminergic drugs have similar effects on sexual function of men and male rats, this information should contribute to better understanding and treatment of human sexual dysfunction.